JPH068239B2 - Liquid phase epitaxial growth method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crystal growth method, and more particularly to a crystal growth by a liquid phase epitaxial method.

[Conventional technology]

Liquid phase epitaxial (LP
Magnetic garnet liquid phase epitaxial film grown by method E) is important for magneto-optical devices. JP-A-57-1
As disclosed in Japanese Patent No. 7919, even if the thickness of this magnetic LPE film is increased, the same performance as that of bulk garnet can be obtained, so that it has been attempted to reduce the cost of bulk, which was expensive in the past. As shown in FIG. 2, the crystal growth method for increasing the thickness of the magnetic garnet film is as follows. The crucible 3 containing the melt 2 is placed in the center of the vertical furnace 1 and the platinum jig 5 is used. Crystal growth is performed by inserting the non-magnetic garnet substrate 4 held by the alumina rod 6 from the upper part of the crucible and immersing it in the melt. Reference numeral 7 is a heater, and 8 is a crucible support.

[Problems to be solved by the invention]

According to this method, after the crystal is completely melted in the crucible, the temperature of the melt is lowered from its liquidus temperature to a supercooled state (temperature state in which crystals can be precipitated) and the supercooled state is maintained for a long time. As a result, when a single crystal film is grown, nuclei of naturally occurring crystal components are precipitated (crystallized) in the melt, and the crystal components dissolved in the melt are reduced. As a result, in the case of the liquid phase epitaxial method, the crystal component in the melt to be grown on the non-magnetic garnet substrate is reduced, so that the growth rate of the single crystal film is attenuated as shown in FIG. Therefore, in a single crystal film grown by maintaining a supercooled state for a long time, such as a garnet thick film, in order to obtain a target film thickness, it is necessary to increase the growth time by reducing the film thickness due to the growth rate decay. This must be compensated for by making it longer, and the growing time becomes longer and productivity decreases.
Further, as shown in FIG. 4, there is a problem that the composition of the single crystal film is not uniform because the composition of the single crystal film is changed due to the change of the growth rate.

An object of the present invention is to provide a liquid phase epitaxial method, in particular, a method in which a vertical furnace is used to insert a substrate from the upper part of the crucible and perform crystal growth on the substrate, and it takes a long time to grow a target film thickness. First, it is to provide a liquid phase epitaxial growth method capable of obtaining a single crystal film having a uniform composition.

[Means for solving problems]

According to the present invention, in a crystal growth method in which a substrate is brought into contact with a melt in a crucible placed in a vertical furnace and a single crystal film is obtained on the substrate by a liquid crystal epitaxial method, the melt in the crucible is In order to prevent the decrease of the growth rate caused by continuing the supercooled state for a long time, the temperature is lowered from the growth start temperature so that the crystal growth rate is constant, and the desired film thickness is grown. A liquid crystal epitaxial growth method is obtained which is characterized by growing a single crystal film having a uniform composition without being prolonged.

〔Example〕

 Next, examples will be described.

Example 1 As shown in FIG. 1, in order to cope with the temporal change of the crystal growth rate such as characteristic 11 by the method of maintaining a supercooled state for a long time, in this example, the crystal growth rate of The crystal growth temperature of the melt in the crucible was lowered as shown in Characteristic 12 in proportion to the temporal change. Therefore, the growth rate is not attenuated by maintaining the supercooled state for a long time, and a constant growth rate can be obtained. Under these conditions, garnet thick film was grown. As a raw material, PbO and B ₂ O ₃ were used as the flux system, and Y ₂ O ₃ and G were used as the garnet components.
d ₂ O ₃ was used. The substrate is Gd ₃ Ga ₅ O _{12 with} a diameter of 1.5 inches and a thickness of
The one with 300 μm was used. The crystal growth temperature was 890 ° C., the crystal growth rate was 0.35 μm / min, and the atmosphere was grown in the atmosphere. For the Gd ₃ Ga ₅ O ₁₂ substrate, only the crystal growth surface was immersed in the melt.
It was rotated at 80 rpm. During the crystal growth, the melt temperature was lowered at a rate of 0.42 ° C./hour in order to keep the growth rate constant against the above growth rate decay. As a result, almost no decrease in the growth rate was observed, and the target film thickness of 500 μm was obtained in 24 hours, and the film was grown in 6 hours shorter than the conventional method. The composition in the film was also uniform.

Example 2 A Gd _2.1 Bi _0.9 Fe _4.7 Al _0.05 Ga _0.25 O ₁₂ thick film was grown under the above conditions. The raw material is PbO, B as flux system
₂ O ₃ and Bi ₂ O ₃ are used, and Gd ₂ O ₃ and Fe are used as garnet components.
₂ O ₃ and Bi ₂ O ₃ were used. The substrate used was Nd ₃ Ga ₅ O _{12 with} a diameter of 1 inch and a thickness of 600 μm. Crystal growth temperature is 720
℃, crystal growth rate 0.15μm / min, atmosphere is N ₂ 10
/ Min began to grow. For the Nd ₃ Ga ₅ O ₁₂ substrate, only the crystal growth surface was immersed in the melt and rotated at 80 rpm. Similar to Example 1, the temperature of the melt was lowered at a rate of 0.3 ° C./min in order to keep the growth rate constant against the growth rate decay of the melt. As a result, almost no decrease in the growth rate was observed, and the target film thickness of 200 μm was obtained in 22 hours, and it grew in 5 hours shorter than the conventional method. The composition in the film was also uniform.

〔The invention's effect〕

As described above, according to the present invention, in the liquid phase epitaxial method, particularly in the method of placing the crucible containing the melt in the vertical furnace and gradually inserting the substrate from the upper part of the crucible to grow crystals, By lowering the temperature of the melt from the temperature at the start of growth so that the growth rate of the single crystal film is constant, the single crystal film is grown, and the target single crystal film thickness is higher than that of the conventional method. It can be obtained in a short time and has a uniform composition in the single crystal film.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the present invention, and is a diagram showing a characteristic 11 showing a growth rate decay due to a time change and a melt temperature characteristic 12 lowered proportionally to eliminate the decay. Is. FIG. 2 is a diagram showing the structure of an LPE furnace (vertical furnace), and FIG. 3 is a diagram for explaining the conventional epitaxial growth method, showing the decay of the growth rate with time. FIG. 4 is a diagram for explaining the conventional epitaxial growth method, and shows that the composition of the garnet component is changed by changing the substitution amount of bismuth according to the change of the growth rate. 1 is LPE furnace (vertical furnace) main body, 2 is melt, 3 is crucible, 4
Is a garnet substrate, 5 is a platinum jig, 6 is an alumina rod, 7
Is a heater and 8 is a crucible support.

Claims (1)

[Claims] 1. A crystal growing method for bringing a substrate into contact with a melt in a crucible placed in a vertical furnace to obtain a single crystal film on the substrate by a liquid phase epitaxial method. At the start of the growth, the temperature is controlled so that the growth rate of the single crystal film is kept constant by suppressing the precipitation of the crystal component nuclei that do not contribute to the growth of the single crystal film on the substrate and precipitate in the melt during the crystal growth. A liquid phase epitaxial method characterized by growing a single crystal film by lowering the temperature.